443 research outputs found

    A New Cutting Device Design to Study the Orthogonal Cutting of CFRP Laminates at Different Cutting Speeds

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    [EN] Carbon Fiber-reinforced plastics (CFRPs) are widely used in the aerospace industry due to their highly mechanical properties and low density. Most of these materials are used in high-risk structures, where the damage caused by machining must be controlled and minimized. The optimization of these processes is still a challenge in the industry. In this work, a special cutting device, which allows for orthogonal cutting tests, with a linear displacement at a wide range of constant cutting speeds, has been developed by the authors. This paper describes the developed cutting device and its application to analyze the influence of tool geometry and cutting parameters on the material damage caused by the orthogonal cutting of a thick multidirectional CFRP laminate. The results show that a more robust geometry (higher cutting edge radius and lower rake angle) and higher feed cause an increase in the thrust force of a cutting tool, causing burrs and delamination damage. By reducing the cutting speed, the components with a higher machining force were also observed to have less surface integrity control.This research was funded by the Ministry of economy, Industry and Competitiveness and FEDER (grant number: DPI2017-89197-C2-1-R).Criado, V.; Feito-SĂĄnchez, N.; Cantero GuisĂĄndez, J.; DĂ­az-Álvarez, J. (2019). A New Cutting Device Design to Study the Orthogonal Cutting of CFRP Laminates at Different Cutting Speeds. Materials. 12(24):1-13. https://doi.org/10.3390/ma12244074S1131224Che, D., Saxena, I., Han, P., Guo, P., & Ehmann, K. F. (2014). Machining of Carbon Fiber Reinforced Plastics/Polymers: A Literature Review. Journal of Manufacturing Science and Engineering, 136(3). doi:10.1115/1.4026526Vigneshwaran, S., Uthayakumar, M., & Arumugaprabu, V. (2018). Review on Machinability of Fiber Reinforced Polymers: A Drilling Approach. Silicon, 10(5), 2295-2305. doi:10.1007/s12633-018-9764-9Panchagnula, K. K., & Palaniyandi, K. (2018). Drilling on fiber reinforced polymer/nanopolymer composite laminates: a review. Journal of Materials Research and Technology, 7(2), 180-189. doi:10.1016/j.jmrt.2017.06.003Wang, F., Yin, J., Ma, J., & Niu, B. (2018). Heat partition in dry orthogonal cutting of unidirectional CFRP composite laminates. Composite Structures, 197, 28-38. doi:10.1016/j.compstruct.2018.05.040FernĂĄndez-PĂ©rez, J., Cantero, J. L., DĂ­az-Álvarez, J., & MiguĂ©lez, M. H. (2017). Influence of cutting parameters on tool wear and hole quality in composite aerospace components drilling. Composite Structures, 178, 157-161. doi:10.1016/j.compstruct.2017.06.043Feito, N., DĂ­az-Álvarez, J., LĂłpez-Puente, J., & Miguelez, M. H. (2018). Experimental and numerical analysis of step drill bit performance when drilling woven CFRPs. Composite Structures, 184, 1147-1155. doi:10.1016/j.compstruct.2017.10.061LĂłpez de Lacalle, L. N., & Lamikiz, A. (2009). Milling of Carbon Fiber Reinforced Plastics. Advanced Materials Research, 83-86, 49-55. doi:10.4028/www.scientific.net/amr.83-86.49Feito, N., Diaz-Álvarez, A., Cantero, J. L., RodrĂ­guez-MillĂĄn, M., & MiguĂ©lez, H. (2015). Experimental analysis of special tool geometries when drilling woven and multidirectional CFRPs. Journal of Reinforced Plastics and Composites, 35(1), 33-55. doi:10.1177/0731684415612931Henerichs, M., Voß, R., Kuster, F., & Wegener, K. (2015). Machining of carbon fiber reinforced plastics: Influence of tool geometry and fiber orientation on the machining forces. CIRP Journal of Manufacturing Science and Technology, 9, 136-145. doi:10.1016/j.cirpj.2014.11.002Yan, X., Reiner, J., Bacca, M., Altintas, Y., & Vaziri, R. (2019). A study of energy dissipating mechanisms in orthogonal cutting of UD-CFRP composites. Composite Structures, 220, 460-472. doi:10.1016/j.compstruct.2019.03.090Lopresto, V., Langella, A., Caprino, G., Durante, M., & Santo, L. (2017). 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An experimental study of orthogonal cutting mechanisms for epoxies with two different crosslink densities. International Journal of Machine Tools and Manufacture, 124, 117-125. doi:10.1016/j.ijmachtools.2017.10.003Lopresto, V., Caggiano, A., & Teti, R. (2016). High Performance Cutting of Fibre Reinforced Plastic Composite Materials. Procedia CIRP, 46, 71-82. doi:10.1016/j.procir.2016.05.079Voss, R., Seeholzer, L., Kuster, F., & Wegener, K. (2019). Analytical force model for orthogonal machining of unidirectional carbon fibre reinforced polymers (CFRP) as a function of the fibre orientation. Journal of Materials Processing Technology, 263, 440-469. doi:10.1016/j.jmatprotec.2018.08.001Seeholzer, L., Voss, R., Grossenbacher, F., Kuster, F., & Wegener, K. (2018). Fundamental analysis of the cutting edge micro-geometry in orthogonal machining of unidirectional Carbon Fibre Reinforced Plastics (CFRP). 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 Wang, R. (2017). Study on Damage Evaluation and Machinability of UD-CFRP for the Orthogonal Cutting Operation Using Scanning Acoustic Microscopy and the Finite Element Method. Materials, 10(2), 204. doi:10.3390/ma10020204Sahraie Jahromi, A., & Bahr, B. (2010). An analytical method for predicting cutting forces in orthogonal machining of unidirectional composites. Composites Science and Technology, 70(16), 2290-2297. doi:10.1016/j.compscitech.2010.09.005Wang, D. H., Ramulu, M., & Arola, D. (1995). Orthogonal cutting mechanisms of graphite/epoxy composite. Part I: unidirectional laminate. International Journal of Machine Tools and Manufacture, 35(12), 1623-1638. doi:10.1016/0890-6955(95)00014-oLi, H., Qin, X., He, G., Jin, Y., Sun, D., & Price, M. (2015). Investigation of chip formation and fracture toughness in orthogonal cutting of UD-CFRP. The International Journal of Advanced Manufacturing Technology, 82(5-8), 1079-1088. doi:10.1007/s00170-015-7471-xVoss, R., Seeholzer, L., Kuster, F., & Wegener, K. (2017). Influence of fibre orientation, tool geometry and process parameters on surface quality in milling of CFRP. CIRP Journal of Manufacturing Science and Technology, 18, 75-91. doi:10.1016/j.cirpj.2016.10.002Nayak, D., Bhatnagar, N., & Mahajan, P. (2005). MACHINING STUDIES OF UNI-DIRECTIONAL GLASS FIBER REINFORCED PLASTIC (UD-GFRP) COMPOSITES PART 1: EFFECT OF GEOMETRICAL AND PROCESS PARAMETERS. Machining Science and Technology, 9(4), 481-501. doi:10.1080/10910340500398167An, Q., Cai, C., Cai, X., & Chen, M. (2019). Experimental investigation on the cutting mechanism and surface generation in orthogonal cutting of UD-CFRP laminates. Composite Structures, 230, 111441. doi:10.1016/j.compstruct.2019.111441Bhatnagar, N., Nayak, D., Singh, I., Chouhan, H., & Mahajan, P. (2004). Determination of Machining-Induced Damage Characteristics of Fiber Reinforced Plastic Composite Laminates. Materials and Manufacturing Processes, 19(6), 1009-1023. doi:10.1081/amp-200035177Wang, X., Kwon, P. Y., Sturtevant, C., Kim, D. (Dae-W., & Lantrip, J. (2013). Tool wear of coated drills in drilling CFRP. Journal of Manufacturing Processes, 15(1), 127-135. doi:10.1016/j.jmapro.2012.09.019FernĂĄndez-PĂ©rez, J., Cantero, J. L., Álvarez, J. D., & MiguĂ©lez, M. H. (2017). Composite Fiber Reinforced Plastic one-shoot drilling: Quality inspection assessment and tool wear evaluation. Procedia Manufacturing, 13, 139-145. doi:10.1016/j.promfg.2017.09.021Sorrentino, L., Turchetta, S., Colella, L., & Bellini, C. (2016). Analysis of Thermal Damage in FRP Drilling. Procedia Engineering, 167, 206-215. doi:10.1016/j.proeng.2016.11.689DĂ­az-Álvarez, J., Criado, V., MiguĂ©lez, H., & Cantero, J. (2018). PCBN Performance in High Speed Finishing Turning of Inconel 718. Metals, 8(8), 582. doi:10.3390/met8080582Su, Y. (2019). Effect of the cutting speed on the cutting mechanism in machining CFRP. Composite Structures, 220, 662-676. doi:10.1016/j.compstruct.2019.04.052Wang, X. M., & Zhang, L. C. (2003). An experimental investigation into the orthogonal cutting of unidirectional fibre reinforced plastics. International Journal of Machine Tools and Manufacture, 43(10), 1015-1022. doi:10.1016/s0890-6955(03)00090-7Xu, J., El Mansori, M., Voisin, J., Chen, M., & Ren, F. (2019). On the interpretation of drilling CFRP/Ti6Al4V stacks using the orthogonal cutting method: Chip removal mode and subsurface damage formation. Journal of Manufacturing Processes, 44, 435-447. doi:10.1016/j.jmapro.2019.05.05

    Efecto de diferentes formulaciones de carga de fondo en flujos transitorios con lecho mĂłvil

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    El objetivo de este trabajo es realizar un estudio comparativo entre diferentes formulaciones de carga de fondo (GarcĂ­a, 2008), y su efecto en transitorios con lecho mĂłvil, tomando como caso de estudio la rotura de presa, a travĂ©s de la modificaciĂłn empĂ­rica propuesta por Wu y Wang (2007). Para ello se emplean las ecuaciones de Saint-Venant para lecho mĂłvil desarrolladas por Wu y Wang (2007), las cuales se resuelven mediante el uso de un esquema de volĂșmenes finitos

    Use of “clickers” in practical sessions: Civil Engineering and History Degrees

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    Este trabajo presenta un estudio sobre el rendimiento y la motivaciĂłn de los estudiantes de grado en la Universidad de CĂłrdoba a travĂ©s de la implementaciĂłn de clickers durante las sesiones de prĂĄcticas. Nuevas metodologĂ­as a aplicar durante las sesiones prĂĄcticas en ingenierĂ­a civil basadas en el uso de clickers son desarrolladas en este trabajo. Para medir el impacto de estas nuevas metodologĂ­as, se elabora y se presenta un diseño pretest-postest que se aplicĂł a los estudiantes de tercer curso del grado en ingenierĂ­a civil en la Universidad de CĂłrdoba. Finalmente, los estudiantes de tercer curso del grado de IngenierĂ­a civil y los procedentes del primer curso del grado en Historia completaron cuestionarios de satisfacciĂłn para medir el grado de motivaciĂłn con respecto al uso de las nuevas metodologĂ­as y clickers en las sesiones prĂĄcticas. Los resultados de esta experiencia piloto demuestran una mejorĂ­a en el rendimiento motivado por un feedback casi instantĂĄneo, donde un recordatorio conceptual al comienzo de las sesiones juega un papel fundamental. La motivaciĂłn de los estudiantes hacia el uso de clickers en las sesiones prĂĄcticas es elevada y notable. Tanto la motivaciĂłn como la atenciĂłn son potenciadas por el uso del recordatorio conceptual al comienzo de las sesiones prĂĄcticas y, por tanto, se recomienda su aplicaciĂłn.This work studies the impact on students’ performance of inserting student-response-systems in practical lessons at the University of CĂłrdoba. Innovative methodologies based on student-response-systems has been developed to be implemented during practical lessons in higher education. A pretest-posttest design is developed and presented in this work to assess the evolution in performance by the students of third course in Civil Engineering Grade at the University of CĂłrdoba during a single course. Finally, motivational questionnaire towards the use of the innovative methodologies and clikers are filled by the students belonging to both Civil Engineering and History grades. The results of this pilot experience show a positive impact on the students’ performance by a rapid feedback, in which a conceptual reminder at the beginning of the practical lessons allow to boost the enhancement. The motivational questionnaires described an overall positive students’ awareness of the use of the methodologies and clickers. Both motivation and engagement are boosted by the application of the conceptual reminder at the beginning of the practical lessons and, therefore, its consideration is recommended

    Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

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    We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

    Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

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    This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

    Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

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    The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

    Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

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    A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

    Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

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    A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters
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